LSD on a 4x4 Dually?

[SmokeyWren]

Originally Posted by RussOnTheRoad

I'm wondering how that would interplay with an LSD, if it obviates the need for an LSD, and still if I should opt for the LSD or open differential?!?

Traction control is now standard on the 2017 F-350 DRW. But it has nothing to do with adding traction for pulling a heavy trailer on slick roads.

Traction control means reducing engine power or brake force applied to one or more wheels to stop the tires from slipping. If the system senses you are losing traction on one tire, it reduces engine power (torque), or applies the brakes on the slipping tire, or both reduced power and increased braking, until the rig slows down enough to regain traction.

So yes, you need a limited-slip rear differential (LSD) if you plan to be towing on slick roads. Millions of vehicles have survived without a limited slip rear axle, but it's so much more pleasant to drive a vehicle that can keep all rear tires pulling. An electronic locking rear diff is even better than LSD, but if it's not available, then you want the LSD.

Even with LSD, if your rear end begins to slip because of the slick stuff, then traction control will take over and reduce power or increase braking to the slipping tires.

Way back over 52 years ago, I ordered a new 1965 Corvette Stingray coupe and my only options were 4-speed tranny and Posi-Traction (GM's name for LSD.) Yes, back then, a 3-speed manual transmission was standard on the Corvette, and only car nuts knew about Posi-Traction.

[RussOnTheRoad]

Originally Posted by Parks

Don't know the Ford product too well but the Traction Control and LSD should have anything to do with each other. You know what the LSD should do with regards to wheel slippage and activating the other side. The TC will govern the engine if it senses wheel slippage. Basically TCwould never allow you to "burn rubber".

Actually, traction control on the new Super Duty is described this way in the owners manual:

"If your vehicle begins to slide, the system applies the brakes to individual wheels and, when needed, reduces engine power at the same time. If the wheels spin when accelerating on slippery or loose surfaces, the system reduces engine power in order to increase traction."

So, it appears its more than just slowing the engine and in fact application of one or more brakes may precede RPM reduction of the engine.

You can see why I wonder about the interplay of TC and an LSD as they both are designed to reduce wheel spin.

[L.C.Gray]

Originally Posted by SmokeyWren

You're confusing the ESOF (electronic shift on the fly) option that locks or unlocks the front hubs. It has nothing to do with the rear axle, and it dos not mean that the front axle is locked. Without the front hubs locked, you don't have 4x4 capability, so in effect you have a 4x2 truck.

Nope, the E locker in the rear axle as a second function off the same ESOF knob. Works in both 2 and 4 wheel drive. You pull it and she's locked up!

"One of the best options in the 2011 Super Duty is the addition the electronic locking rear differential for the first time that's similar to the GKN-supplied e-locker, which is available on the FX4 Off-Road package (and SVT Raptor). The "3.73 ELECTRONIC LOCKING AXLE." is $390.00 Option.

The e-locker has been designed by Ford and is manufactured at the Sterling Axle plant for single-rear-wheel F-Series Super Duty trucks only.

The locker is controlled with a factory dash switch. It's best used in low-friction scenarios, such as on slippery boat ramps or in slick mud and on icy roads. It will stays engaged until the truck reaches 30 mph, at which point it disengages until the truck's speed returns to 30 mph or less. The truck will also disengage the locker if it's making a tight radius turn by sensing the steering wheel position, so the rear wheels and tires aren't damaged from scrubbing on pavement. In summary it will get your truck out of that "Stuck When Plowing" situation that arises a few times a year! (Note: Some 2010 F-150's have this option, but for SuperDuty 2011 was the first year."

Front hubs on modern SD's are vacuum actuated or can be manually locked at the hubs

[L.C.Gray]

Originally Posted by RussOnTheRoad

Locking axles are available on Ford Super Duty trucks but this appears to be true only for SRW vehicles and not duallies. I have the brochure in front of me.

Shortly after I posted about lockers being available in the SD line, I became aware the dually's are excluded. I find that rather amazing...

[MtnTrek]

Originally Posted by chertz

Dually's tend to be "hogs on ice" when unloaded... with such a heavy front end I have seen 2wd Duallies with open diffs get stuck in wet grass or dropping the front wheels off the driveway. 4x4 and LSD in the rear for me. And Yes, I have had to use 4x4 once to get out of wet grass once before I got new tires!

LOL, isn't that the truth. I remember my first Dodge CTD back in the late nineties. I was so proud of that gem, pulled my boat so well, til the first time eased off into a muddy pasture. That nose heavy hog with the iron CTD block, it marred down to the front axles quickly. Live and learn.

[Parks]

Originally Posted by RussOnTheRoad

Actually, traction control on the new Super Duty is described this way in the owners manual:

"If your vehicle begins to slide, the system applies the brakes to individual wheels and, when needed, reduces engine power at the same time. If the wheels spin when accelerating on slippery or loose surfaces, the system reduces engine power in order to increase traction."

So, it appears its more than just slowing the engine and in fact application of one or more brakes may precede RPM reduction of the engine.

You can see why I wonder about the interplay of TC and an LSD as they both are designed to reduce wheel spin.

The two systems, for the most part, are completely different and don't "interplay. If you are in a situation whether stuck in a snow bank or other situation the LSD will allow both wheels to spin to get the mos traction. If you have your Traction Control engaged while in this same situation it will not allow you to get the engine revved and tires spinning. As soon as the vehicle senses wheel slippage it cuts power to the wheels. You are then stuck.

TC is good for higher speeds where questionable traction exists. Helps keep your truck from sliding off the interstate in snowy or wet weather. TC at slow speeds, off-roading or or on slippery surfaces is terrible.

[SmokeyWren]

Originally Posted by L.C.Gray

Nope, the E locker in the rear axle as a second function off the same ESOF knob. Works in both 2 and 4 wheel drive. You pull it and she's locked up!

But the e-locker rear axle is not available in an F-350 DRW. Open axle is standard, and limited-slip (LS) is an option. So the ESOF switch does nothing about locking the rear axle.

[L.C.Gray]

Originally Posted by SmokeyWren

But the e-locker rear axle is not available in an F-350 DRW. Open axle is standard, and limited-slip (LS) is an option. So the ESOF switch does nothing about locking the rear axle.

I don't have a DRW. I have a factory E Lock and pulling out the ESOF knob locks the rear end whether in 2x or 4x so whistle all you want...

[Off Road]

Originally Posted by Parks

The two systems, for the most part, are completely different and don't "interplay. If you are in a situation whether stuck in a snow bank or other situation the LSD will allow both wheels to spin to get the mos traction. If you have your Traction Control engaged while in this same situation it will not allow you to get the engine revved and tires spinning. As soon as the vehicle senses wheel slippage it cuts power to the wheels. You are then stuck.

TC is good for higher speeds where questionable traction exists. Helps keep your truck from sliding off the interstate in snowy or wet weather. TC at slow speeds, off-roading or or on slippery surfaces is terrible.

The last paragraph above is key for anyone who has traction control. I buried my new Dodge Cummins last year on an elk hunt, in a muddy stream crossing in Montana. The TC cut in and I lost all power and so couldn't power through the soft spot. Subsequent reading in the owners manual described a very important switch that I now turn off every time I am putting around on Forest Service and BLM roads.

[MtnTrek]

Yeah any doubt, just turn that TC switch off and check out what 900 ft/lbs. Torque can do unleashed. TeeHee, hook'er up!

https://www.youtube.com/watch?v=8omTtVE7MC4

[Parks]

Originally Posted by Off Road

The last paragraph above is key for anyone who has traction control. I buried my new Dodge Cummins last year on an elk hunt, in a muddy stream crossing in Montana. The TC cut in and I lost all power and so couldn't power through the soft spot. Subsequent reading in the owners manual described a very important switch that I now turn off every time I am putting around on Forest Service and BLM roads.

Yep. Had a relative get stuck I his fancy SUV years ago. Lexus or Infinity or something. Couldn't figure out how to turn off the TC so we had to yank him up the snowy/icy hill and driveway.

I would recommend all the truck owners with the TV feature to not only read the owners manual but do an Internet search on how to properly turn off the TC in your model truck. I believe some trucks "buttons" don't turn the TC off all the way, so to speak. Sometimes more than just a button is needed to make it go away, fully.

[Duoglide1]

Now I'm going to have to check mine. I have a button on the dash but if I'm not mistaken when I select 4wd I believe the TSC Off light comes on automatically. 2016 F350 dually.

[wingnut60]

Yep, the TC is off when 4x4 is selected...

[rskeans]

My '92 Ford Bronco had a LSD in the front differential. It was kind of a nuscience (sp) as it always was fighting you when you needed to turn the wheel such as in the mountains.